This invention relates to a catheter having a head at its end which is used for administration of nutrient or liquid medicine by orally or nasally inserting it into the digestive tract and indwelling there.
Catheters adapted to be orally or nasally inserted into the digestive tract and indwelled there for feeding nutrient are generally called "nutritive catheters". A suitable leading member is attached to the distal end of a tube which is formed near the distal end with an opening for passage of nutrient fed through the tube duct. There are known in the prior art a variety of such catheters modified so as to facilitate their passage through the esophagus and pylorus, for example, one having a mercury bag at the distal end, one having a metal head at the distal end, and one having metal beads sealed in the tube end (see Japanese Utility Model Application Kokai No. 57-21341, Japanese Utility Model Publication No. 57-44995, and Japanese Utility Model Application Kokai No. 57-36944).
FIG. 2 shows one example of the prior art nutritive catheters in which a head in the form of a bag 5 filled with mercury 6 is attached to the distal end of a main tube 9. The catheter shown in FIG. 3 has a solid metal head 7 attached to the distal end of a main tube 9. A further example of catheter is shown in FIG. 4 as comprising metal beads 8 sealed in the distal end portion of a main tube 9. In all these catheters, an opening 2 for discharging liquid medicine is perforated in the main tube 9.
Attachement of a mercury bag is undesirable in safety because mercury flows out upon breakage or detachment of the bag. A metal head is also dangerous as it can be detached.
In addition, the metal head is difficult to insert as it does not deform in accordance with the insertion path because of hardness. Sealing of metal beads in a tube end is free of such risks as detachment, but requires a more complicated manufacture process with an increased cost.
In all these catheters, the distal end portion of the tube apart from the leading head is formed with a side opening. That portion of the tube where such an opening is present is mechanically weak so that the tube is likely to bend, inviting difficulty of insertion or blockage of flow duct.
There are known some catheters having a radiopaque substance incorporated therein such as lead, barium, bismuth and tungsten compounds. The radiopaque substances usually have a specific gravity of less than 2 and are unsuitable as a weight because they are simply expected to provide contrast effect. Some ferrite-filled materials have a specific gravity of more than 2. Such a high specific gravity is given by incorporating a larger proportion of ferrite. The resulting leading member for a nutritive catheter is too hard to perform as a medical weight requiring flexibility.